Reservation against PNR NO.811-7024715

I,Utkarsh Pande,student of ist year,engg. at SSCET,Bhilai had taken a reservation from nashik road to durg on 14.01.08 from train no.2809.I went to nashik stn. for cancellaion of my ticket on this date. But ,I, to my surprise, was told that " a duplicate ticket has been taken by some other person .Hence it cannot be cancelled."The original ticket is already available with me .So i request for investigating the matter and refund me the due amount.